It is known in modern automobile manufacture to use a laminated steel panel that is formed to shape in a conventional metal stamping press. Laminated steel is manufactured by bonding together a first steel sheet and a second steel sheet by a layer of polymer material that is cured in place between the first and second metal sheets to thereby attach the sheets together. The polymer has viscoelastic properties that dampen the transmission of noise and vibration through the panel.
In the factory, the laminated steel panels can be successfully attached to vehicle structures such as tubular members by squeeze-type resistance spot welding. The factory environment of mass production enables process and quality control procedures that facilitate making of the welds.
However, in the collision repair environment it is often difficult to access the vehicle structure with squeeze type resistance spot welding equipment. Additionally, because the thickness of the steel layers and the polymer layers will vary between vehicle models and between vehicle manufacturers, the typical collision repair shop may experience a wide variation of material thickness which in turn requires a wide range of welder settings, so that the making of test welds may be needed. In addition, the electric resistance spot welding is made difficult by the fact that the polymer material is a dielectric and will not conduct electricity.
The industry standard joining process in the collision repair industry is metal inert gas (MIG) plug welding. In MIG plug welding a hole is cut in the laminated steel and then the MIG weld is formed between the laminated steel and the workpiece that underlies the laminated steel. However the polymer layer tends to melt and mix with the weld.
It would be desirable to provide an improved welding process for attaching a laminated steel panel to a vehicle body member, particularly in making collision repairs to a vehicle.